path: root/Documentation/userspace-api/ioctl/hdio.rst

==============================
Summary of `HDIO_` ioctl calls
==============================

- Edward A. Falk <efalk@google.com>

November, 2004

This document attempts to describe the ioctl(2) calls supported by
the HD/IDE layer.  These are by-and-large implemented (as of Linux 2.6)
in drivers/ide/ide.c and drivers/block/scsi_ioctl.c

ioctl values are listed in <linux/hdreg.h>.  As of this writing, they
are as follows:

    ioctls that pass argument pointers to user space:

	=======================	=======================================
	HDIO_GETGEO		get device geometry
	HDIO_GET_UNMASKINTR	get current unmask setting
	HDIO_GET_MULTCOUNT	get current IDE blockmode setting
	HDIO_GET_QDMA		get use-qdma flag
	HDIO_SET_XFER		set transfer rate via proc
	HDIO_OBSOLETE_IDENTITY	OBSOLETE, DO NOT USE
	HDIO_GET_KEEPSETTINGS	get keep-settings-on-reset flag
	HDIO_GET_32BIT		get current io_32bit setting
	HDIO_GET_NOWERR		get ignore-write-error flag
	HDIO_GET_DMA		get use-dma flag
	HDIO_GET_NICE		get nice flags
	HDIO_GET_IDENTITY	get IDE identification info
	HDIO_GET_WCACHE		get write cache mode on|off
	HDIO_GET_ACOUSTIC	get acoustic value
	HDIO_GET_ADDRESS	get sector addressing mode
	HDIO_GET_BUSSTATE	get the bus state of the hwif
	HDIO_TRISTATE_HWIF	execute a channel tristate
	HDIO_DRIVE_RESET	execute a device reset
	HDIO_DRIVE_TASKFILE	execute raw taskfile
	HDIO_DRIVE_TASK		execute task and special drive command
	HDIO_DRIVE_CMD		execute a special drive command
	HDIO_DRIVE_CMD_AEB	HDIO_DRIVE_TASK
	=======================	=======================================

    ioctls that pass non-pointer values:

	=======================	=======================================
	HDIO_SET_MULTCOUNT	change IDE blockmode
	HDIO_SET_UNMASKINTR	permit other irqs during I/O
	HDIO_SET_KEEPSETTINGS	keep ioctl settings on reset
	HDIO_SET_32BIT		change io_32bit flags
	HDIO_SET_NOWERR		change ignore-write-error flag
	HDIO_SET_DMA		change use-dma flag
	HDIO_SET_PIO_MODE	reconfig interface to new speed
	HDIO_SCAN_HWIF		register and (re)scan interface
	HDIO_SET_NICE		set nice flags
	HDIO_UNREGISTER_HWIF	unregister interface
	HDIO_SET_WCACHE		change write cache enable-disable
	HDIO_SET_ACOUSTIC	change acoustic behavior
	HDIO_SET_BUSSTATE	set the bus state of the hwif
	HDIO_SET_QDMA		change use-qdma flag
	HDIO_SET_ADDRESS	change lba addressing modes

	HDIO_SET_IDE_SCSI	Set scsi emulation mode on/off
	HDIO_SET_SCSI_IDE	not implemented yet
	=======================	=======================================


The information that follows was determined from reading kernel source
code.  It is likely that some corrections will be made over time.

------------------------------------------------------------------------------

General:

	Unless otherwise specified, all ioctl calls return 0 on success
	and -1 with errno set to an appropriate value on error.

	Unless otherwise specified, all ioctl calls return -1 and set
	errno to EFAULT on a failed attempt to copy data to or from user
	address space.

	Unless otherwise specified, all data structures and constants
	are defined in <linux/hdreg.h>

------------------------------------------------------------------------------

HDIO_GETGEO
	get device geometry


	usage::

	  struct hd_geometry geom;

	  ioctl(fd, HDIO_GETGEO, &geom);


	inputs:
		none



	outputs:
		hd_geometry structure containing:


	    =========	==================================
	    heads	number of heads
	    sectors	number of sectors/track
	    cylinders	number of cylinders, mod 65536
	    start	starting sector of this partition.
	    =========	==================================


	error returns:
	  - EINVAL

			if the device is not a disk drive or floppy drive,
			or if the user passes a null pointer


	notes:
		Not particularly useful with modern disk drives, whose geometry
		is a polite fiction anyway.  Modern drives are addressed
		purely by sector number nowadays (lba addressing), and the
		drive geometry is an abstraction which is actually subject
		to change.  Currently (as of Nov 2004), the geometry values
		are the "bios" values -- presumably the values the drive had
		when Linux first booted.

		In addition, the cylinders field of the hd_geometry is an
		unsigned short, meaning that on most architectures, this
		ioctl will not return a meaningful value on drives with more
		than 65535 tracks.

		The start field is unsigned long, meaning that it will not
		contain a meaningful value for disks over 219 Gb in size.




HDIO_GET_UNMASKINTR
	get current unmask setting


	usage::

	  long val;

	  ioctl(fd, HDIO_GET_UNMASKINTR, &val);

	inputs:
		none



	outputs:
		The value of the drive's current unmask setting





HDIO_SET_UNMASKINTR
	permit other irqs during I/O


	usage::

	  unsigned long val;

	  ioctl(fd, HDIO_SET_UNMASKINTR, val);

	inputs:
		New value for unmask flag



	outputs:
		none



	error return:
	  - EINVAL	Called on a partition instead of the whole disk device
	  - EACCES	Access denied:  requires CAP_SYS_ADMIN
	  - EINVAL	value out of range [0 1]
	  - EBUSY	Controller busy




HDIO_GET_MULTCOUNT
	get current IDE blockmode setting


	usage::

	  long val;

	  ioctl(fd, HDIO_GET_MULTCOUNT, &val);

	inputs:
		none



	outputs:
		The value of the current IDE block mode setting.  This
		controls how many sectors the drive will transfer per
		interrupt.



HDIO_SET_MULTCOUNT
	change IDE blockmode


	usage::

	  int val;

	  ioctl(fd, HDIO_SET_MULTCOUNT, val);

	inputs:
		New value for IDE block mode setting.  This controls how many
		sectors the drive will transfer per interrupt.

	outputs:
		none



	error return:
	  - EINVAL	Called on a partition instead of the whole disk device
	  - EACCES	Access denied:  requires CAP_SYS_ADMIN
	  - EINVAL	value out of range supported by disk.
	  - EBUSY	Controller busy or blockmode already set.
	  - EIO		Drive did not accept new block mode.

	notes:
	  Source code comments read::

	    This is tightly woven into the driver->do_special cannot
	    touch.  DON'T do it again until a total personality rewrite
	    is committed.

	  If blockmode has already been set, this ioctl will fail with
	  -EBUSY



HDIO_GET_QDMA
	get use-qdma flag


	Not implemented, as of 2.6.8.1



HDIO_SET_XFER
	set transfer rate via proc


	Not implemented, as of 2.6.8.1



HDIO_OBSOLETE_IDENTITY
	OBSOLETE, DO NOT USE


	Same as HDIO_GET_IDENTITY (see below), except that it only
	returns the first 142 bytes of drive identity information.



HDIO_GET_IDENTITY
	get IDE identification info


	usage::

	  unsigned char identity[512];

	  ioctl(fd, HDIO_GET_IDENTITY, identity);

	inputs:
		none



	outputs:
		ATA drive identity information.  For full description, see
		the IDENTIFY DEVICE and IDENTIFY PACKET DEVICE commands in
		the ATA specification.

	error returns:
	  - EINVAL	Called on a partition instead of the whole disk device
	  - ENOMSG	IDENTIFY DEVICE information not available

	notes:
		Returns information that was obtained when the drive was
		probed.  Some of this information is subject to change, and
		this ioctl does not re-probe the drive to update the
		information.

		This information is also available from /proc/ide/hdX/identify



HDIO_GET_KEEPSETTINGS
	get keep-settings-on-reset flag


	usage::

	  long val;

	  ioctl(fd, HDIO_GET_KEEPSETTINGS, &val);

	inputs:
		none



	outputs:
		The value of the current "keep settings" flag



	notes:
		When set, indicates that kernel should restore settings
		after a drive reset.



HDIO_SET_KEEPSETTINGS
	keep ioctl settings on reset


	usage::

	  long val;

	  ioctl(fd, HDIO_SET_KEEPSETTINGS, val);

	inputs:
		New value for keep_settings flag



	outputs:
		none



	error return:
	  - EINVAL	Called on a partition instead of the whole disk device
	  - EACCES	Access denied:  requires CAP_SYS_ADMIN
	  - EINVAL	value out of range [0 1]
	  - EBUSY		Controller busy



HDIO_GET_32BIT
	get current io_32bit setting


	usage::

	  long val;

	  ioctl(fd, HDIO_GET_32BIT, &val);

	inputs:
		none



	outputs:
		The value of the current io_32bit setting



	notes:
		0=16-bit, 1=32-bit, 2,3 = 32bit+sync





HDIO_GET_NOWERR
	get ignore-write-error flag


	usage::

	  long val;

	  ioctl(fd, HDIO_GET_NOWERR, &val);

	inputs:
		none



	outputs:
		The value of the current ignore-write-error flag





HDIO_GET_DMA
	get use-dma flag


	usage::

	  long val;

	  ioctl(fd, HDIO_GET_DMA, &val);

	inputs:
		none



	outputs:
		The value of the current use-dma flag





HDIO_GET_NICE
	get nice flags


	usage::

	  long nice;

	  ioctl(fd, HDIO_GET_NICE, &nice);

	inputs:
		none



	outputs